Eosinophilic esophagitis (EE) is a chronic allergic disease of increasing prevalence diagnosed as an acid- independent esophageal eosinophilia of >15 per high power field. Esophageal epithelial proliferation, smooth muscle dysmotility, and esophageal strictures are EE associated features. Tissue remodeling with epithelial changes and subepithelial fibrosis occur in EE and involve TGF21, a pro-fibrotic molecule. However, the mechanisms for epithelial and smooth muscle changes are largely unclear; and the genetic factors for a more severe EE phenotype are unknown. There are no surrogate markers for EE. Children must undergo repeated invasive endoscopy with tissue biopsy for diagnosis and management. Our EE center provides the essential patient population and collaborative interactions for studying the mechanisms of EE and for understanding their impact on clinical disease. Our first aim is based on our preliminary studies demonstrating that Cripto-1, a new protein in EE, is increased in the esophageal epithelium of pediatric EE patients. We will use primary esophageal epithelial cells to understand how Cripto-1 increases esophageal epithelial cell proliferation and if Cripto-1 works with TGF2 family members. We will determine the expression of Cripto-1 in the esophagus of EE patients as compared with normal patients and define if Cripto-1 functions as a biomarker for EE. Our second aim is based on our current studies showing the novel findings that the smooth muscle in EE patients is infiltrated by mast cells that produce TGF21 and that TGF21 increases both esophageal smooth muscle cell contraction and phospholamban, a new protein in EE. We will use primary esophageal smooth muscle cells, EE patient myofibroblasts, gene silencing techniques, and a novel application of an in vitro contraction assay to delineate if TGF21 mediated contraction relies on phospholamban. Our third aim is based on our observation that a functional single nucleotide polymorphism (SNP) in the TGF21 promoter (C-509T) is associated with resolution of EE following swallowed topical corticosteroids. SNP analysis on EE patients and controls will be completed to define if the CC genotype associates with a therapy responsive phenotype and if the TT genotype associates with a more severe EE phenotype. Experiments using primary cells from EE patients of CC and TT genotype and chromatin immunoprecipitation for YY-1 will determine in vivo occupation of the TGF21 promoter and promoter activity in EE. These studies are designed to provide innovative techniques and new therapeutic targets for the understanding and care of EE patients.